Sample identification for intra block copy in video coding

Abstract

A method of video processing includes maintaining, for a conversion between a current video block of a current picture of a visual media data and a bitstream representation of the visual media data, a buffer including reference samples from the current picture for a derivation of prediction samples of the current video block. One or more reference samples in the buffer that are marked unavailable for the derivation have values outside of a pixel value range.

What is claimed is: 
     
       1. A method of processing video data, comprising:
 determining, for a conversion between a current video block of a current picture of a video and a bitstream of the video, that a prediction mode is applied on the current video block; 
 maintaining, for the current video block, a buffer comprising reference samples derived from blocks of sample values of a same video region of the current video block in the current picture; 
 generating, for the current video block, prediction samples based on the determining; and 
 performing the conversion between the current video block and the bitstream, 
 wherein in the prediction mode, the reference samples determined by a block vector in the buffer are used for a derivation of prediction samples of the current video block, 
 wherein a specific reference block in the buffer that is marked unavailable for the derivation have values outside of a pixel value range, 
 wherein locations of reference samples in the specific reference block are determined based on a size of a virtural unit, 
 wherein, when the current video block contains one or more virtual units, the locations of the references samples in the specific reference block are determined further based on a size of the current video block, and 
 wherein locations of the reference samples in the specific reference block are determined based on (x0, y0), wherein y0%Vsize=0, (x0, y0) specifies a location in the current picture, where where Vsize denotes the size of the virtual unit, wherein locations of the reference samples in the specific reference block are determined futher based on a value x0%Vsize, and wherein % is a remainder operation. 
 
     
     
       2. The method of  claim 1 , wherein values of reference samples in the specific reference block marked unavailable are set to a predetermined value indicative of unavailability of the samples. 
     
     
       3. The method of  claim 2 , wherein the predetermined value is −1. 
     
     
       4. The method of  claim 2 , wherein a location and a size of the specific reference block marked unavailable are determined based on one or more of: a size of the current video block, a size of a virtual unit, or a size of a coding tree block including the current video block. 
     
     
       5. The method of  claim 4 , wherein (x0%Vsize) is equal to 0,
 Vsize=min(ctbSize, 64), and 
 ctbSize denotes a width or a height of the coding tree block. 
 
     
     
       6. The method of  claim 4 , wherein the size of the specific reference block marked unavailable is determined based on the size of the virtual unit if the size of the current video block is smaller than the size of the virtual unit. 
     
     
       7. The method of  claim 4 , wherein the size of the specific reference block marked unavailable is determined based on the size of the current video block if the size of the current video block is larger than the size of the virtual unit. 
     
     
       8. The method of  claim 1 , wherein the buffer is reset before coding a picture or a slice. 
     
     
       9. The method of  claim 1 , wherein a bitstream conformance constraint satisfied by the bitstream comprises the reference samples determined by the block vector in the buffer not having values equal to a predetermined value indicative of unavailability of the samples. 
     
     
       10. The method of  claim 1 , wherein the pixel value range is expressed as [0, 1<<(bit_depth)−1], where bit_depth is a positive integer. 
     
     
       11. The method of  claim 10 , wherein bit_depth is a precision used for processing the sample. 
     
     
       12. The method of  claim 1 , wherein the conversion includes encoding the current video block into the bitstream. 
     
     
       13. The method of  claim 1 , wherein the conversion includes decoding the current video block from the bitstream. 
     
     
       14. An apparatus for processing video data comprising a processor and a non-transitory memory with instructions thereon, wherein the instructions upon execution by the processor, cause the processor to:
 determine, for a conversion between a current video block of a current picture of a video and a bitstream of the video, that a prediction mode is applied on the current video block; 
 maintain, for the current video block, a buffer comprising reference samples derived from blocks of sample values of a same video region of the current video block in the current picture; 
 generate, for the current video block, prediction samples based on the determining; and 
 perform the conversion between the current video block and the bitstream, 
 wherein in the prediction mode, the reference samples determined by a block vector in the buffer are used for a derivation of prediction samples of the current video block, 
 wherein a specific reference block in the buffer that is marked unavailable for the derivation have values outside of a pixel value range, 
 wherein locations of reference samples in the specific reference block are determined based on a size of a virtural unit, 
 wherein, when the current video block contains one or more virtual units, the locations of the references samples in the specific reference block are determined further based on a size of the current video block, and 
 wherein locations of the reference samples in the specific reference block are determined based on (x0, y0), wherein y0%Vsize=0, (x0, y0) specifies a location in the current picture, where Vsize denotes the size of the virtual unit, wherein locations of the reference samples in the specific reference block are determined futher based on a value x0%Vsize, and wherein % is a remainder operation. 
 
     
     
       15. The apparatus of  claim 14 , wherein the values of reference samples in the specific reference block marked unavailable are set to a predetermined value indicative of unavailability of the samples. 
     
     
       16. The apparatus of  claim 15 , wherein the predetermined value is −1. 
     
     
       17. The apparatus of  claim 15 , wherein a location and a size of the specific reference block marked unavailable are determined based on one or more of: a size of the current video block, a size of a virtual unit, or a size of a coding tree block including the current video block. 
     
     
       18. The apparatus of  claim 17 , wherein (x0%Vsize) is equal to 0 and (y0%Vsize) is equal to 0,
 Vsize=min(ctbSize, 64), and 
 ctbSize denotes a width or a height of the coding tree block. 
 
     
     
       19. A non-transitory computer-readable storage medium storing instructions that cause a processor to:
 determine, for a conversion between a current video block of a current picture of a video and a bitstream of the video, that a prediction mode is applied on the current video block; 
 maintain, for the current video block, a buffer comprising reference samples derived from blocks of sample values of a same video region of the current video block in the current picture; 
 generate, for the current video block, prediction samples based on the determining; and 
 perform the conversion between the current video block and the bitstream, 
 wherein in the prediction mode, the reference samples determined by a block vector in the buffer are used for a derivation of prediction samples of the current video block, 
 wherein a specific reference block in the buffer that is marked unavailable for the derivation have values outside of a pixel value range, 
 wherein locations of reference samples in the specific reference block are determined based on a size of a virtural unit, 
 wherein, when the current video block contains one or more virtual units, the locations of the reference samples in the specific reference block are determined further based on a size of the current video block, and 
 wherein locations of the reference samples in the specific reference block are determined based on (x0, y0), wherein y0%Vsize=0, (x0, y0) specifies a location in the current picture, where Vsize denotes the size of the virtual unit, wherein locations of the reference samples in the specific reference block are determined futher based on a value x0%Vsize, and wherein % is a remainder operation. 
 
     
     
       20. A method for storing a bitstream of a video, wherein the method comprises:
 determining, that a prediction mode is applied on the current video block of a current picture of a video; 
 maintaining, for the current video block, a buffer comprising reference samples derived from blocks of sample values of a same video region of the current video block in the current picture; 
 generating, for the current video block, prediction samples based on the determining; and 
 generating the bitstream based on the prediction samples; and 
 storing the bitstream in a non-transitory computer-readable recording medium, 
 wherein in the prediction mode, the reference samples determined by a block vector in the buffer are used for a derivation of prediction samples of the current video block, 
 wherein a specific reference block in the buffer that is marked unavailable for the derivation have values outside of a pixel value range, 
 wherein locations of reference samples in the specific reference block are determined based on a size of a virtural unit, 
 wherein, when the current video block contains one or more virtual units, the locations of the references samples in the specific reference block are determined further based on a size of the current video block, and 
 wherein locations of the reference samples in the specific reference block are determined based on (x0, y0), wherein y0%Vsize=0, (x0, y0) specifies a location in the current picture, where Vsize denotes the size of the virtual unit, wherein the locations of the reference samples in the specific reference block are determined futher based on a value x0%Vsize, and wherein % is a remainder operation.